1. Field of the Invention.
The present invention is directed toward the compact, quality optical transmission of selected images from one location to another, and more particularly toward an optical arrangement for quality transmission of said images along a non-linear path, and their ultimate, collimated presentation with a broad field of view and as though they were located at infinity.
A patent application for a related invention, "Helmet Mounted Display with Improved Brightness", Ser. No. 07/078,947, was filed by the same assignee as herein, Honeywell, Inc., on July 29, 1987, based upon a concept developed by Donald J. Rotier. This application is hereby expressly incorporated herein by reference.
2. Background, Objects and Description of the Prior Art
It is frequently desirable to produce an optical arrangement of elements, which transmits selected images from one location, where they are produced, to another location, where they are conveniently viewed.
In many instances, it is further desirable for the optical arrangement to be compact in order to conserve space, and to maintain the highest possible level of image quality.
In addition to optimizing image quality, it is frequently desired to present the image transmitted with a large field of view.
Further, in order to minimize viewer fatigue, it is desirable for the image ultimately presented, to be produced in collimated fashion, i.e., as though it were located at infinity. For example, in the case of a pilot scanning the horizon and the scene around his plane or helicopter, it creates fatigue for the pilot to have to refocus every time he glances at his instruments for information as to flight conditions. If this information or part of it is presented properly, with a broad field of view and as though at infinity, the pilot will not need not refocus and search repeatedly for the information desired.
In one particular arrangement of the prior art, it is desired for the pilot to view an image which is transmitted from a cathode ray tube ("CRT") mounted on the side of his helmet to his eye. The optical arrangement employed is complex in construction, as it requires the careful construction and precise alignment and positioning of a large number of optical elements in a compact, tubular containment which takes several bends around the face of the pilot as mounted on the helmet. To design and manufacture such an arrangement involves the critical step of initially taking a correct approach in the selection of particular components and elements in the arrangement and then applying well-known, straight forward optical design techniques, including computer simulations, to correct the image aberrations caused by the selected elements.
It is thus a particular object of the invention herein to correctly select key optical elements in the arrangement and to effectively design the remainder of the arrangement to contain all of the optical elements of the arrangement within narrow, confined spaces along a folded path.
Because of the limitations inherent in the selection of particular elements for image translation, present approaches to this problem are generally only effective for producing images with a moderate field of view. Such approaches are further often hampered by undue divergence of light along the optical path through which the images are transmitted.
One arrangement of the prior art, which is hampered as indicated above, includes in the optical arrangement, several turn prisms for changing the direction of the light rays. The use of such positive elements in systems with a wide field of view has a very deleterious effect on the quality of the images presented to the viewer. In addition, depending upon the particular adjacent optical element employed for image quality improvement, the combination can be very difficult to properly align, assemble and construct.